the film

Extra-Large Fall Run
Expected in Columbia and Snake

by Bill Rudolph
NW Fishletter, August 5, 2011

"We're seeing high levels of mortality in the reservoirs," he said.

Snake River Chinook and Steelhead In-River Survival Estimates 1964-2010 When fish counters officially began tallying fall chinook at Bonneville Dam on Aug. 1, it looked like they would get a bigger workout than last year, when they counted nearly half a million fall chinook passing by their windows.

In an annual report released July 13, harvest managers stuck to their March pre-season estimate of 767,000 falls returning to the mouth of the river. That's about 30 percent better than the 10-year average and 17 percent higher than last year's excellent return of 657,000 fall chinook, which includes lower river returns.

Managers expect nearly 400,000 upriver brights (325,000 last year). The report said the expected return of upriver brights would be the highest observed since 1987 and second highest since 1964.

They also estimated that 17,500 wild ESA-listed falls would be heading for the Snake River, which would make it the highest return since the ESU was listed in 1992. Last year, about 15,400 wild fall chinook were estimated to have returned (Columbia River mouth) when only about 5,000 were expected.

Harvest managers also predicted that 136,000 lower river hatchery chinook and 12,500 lower river wilds will return. Last year, about 91,000 lower river hatchery fish showed up, along with 10,900 wilds.

About 116,000 Bonneville hatchery tules are also slated to return, a little less than last year's 131,000.

USFWS researcher Billy Connor, who works at the agency's Dworshak research facility in Idaho, told NW Fishletter that a high percentage of last year's return to the Snake was made up of first generation hatchery fish that spawned successfully in the wild. But it will likely take years more of research before it is known just how successful the hatchery fish are at supplementing the run, which had dipped as low as 78 fish in the early 1970s. He said it's hard enough just to develop what biologists call "run reconstructions" to determine how many wild and hatchery adults pass Lower Granite Dam.

"There are so many differently tagged groups, plus not all the hatchery fish are marked," said Connor. But scientists are still trying to develop a uniform method to analyze returns back to 1998.

"There are probably more hatchery fish on the spawning grounds in the Snake and Clearwater than any other place in the whole basin," Connor said. He noted that the situation makes it even tougher for wild fish to mate with their own kind, when there are seven or eight hatchery fish for every two to three wild ones on the spawning grounds.

He said NOAA Fisheries won't de-list the fish until there is better evidence of increased natural productivity. Anecdotally, he sees evidence that productivity has improved quite a bit, which he credits to improved inriver migrating conditions for juveniles, better ocean productivity and more hatchery releases.

"Back in the '90s, we used to get six to 12 fish a haul in our beach seines. Now we're getting 40 to 60 fish a haul," he said.

'There are probably more hatchery fish on the spawning grounds in the Snake and Clearwater than any other place in the whole basin.'

Another line of research that looks at the genetics of returning fish has been put on the back burner, Connor said. Sample sizes were small, but WDFW researcher Anne Marshall had found the young fish produced in the wild now have a genetic profile that has merged with the profile from the Lyons Ferry hatchery stock.

Connor said the true test of whether supplementation works would be to quit doing it for a while. But that probably won't happen anytime soon, since the U.S. v. Oregon process that governs tribal harvest regimes in the basin calls for certain levels of fall chinook hatchery releases through 2017.

However, he said, discussions are taking place about the possibility of picking one area where supplementation could be stopped and monitoring the results. But other problems complicate that condition, said Connor. "There is the question of whether you can get enough data, and there is always the straying issue. No place is really isolated," he said.

Connor said he didn't expect any definitive answers before he retires in the next 10 to 15 years.

But recent research has turned up several new wrinkles that could impact future returns. Connor said growing evidence shows that the high numbers of juvenile hatchery fall chinook released in the Snake has led to increased predator populations of smallmouth bass and catfish.

"We're seeing high levels of mortality in the reservoirs," he said.

The hatchery fall chinook released in the colder Clearwater River still tend to stay behind compared to their Snake River cousins, said Conner, who was one of the first regional scientists to notice such behavior. About 20 percent remain behind to overwinter in the reservoir, and an unknown number that make it to the Columbia estuary still spend the winter there before entering the ocean the following spring.

The later-migrating fall chinook have made up about 45 percent of returning adults in recent years, Connor said. That could change, because the added spill since 2006 may be flushing more fish downstream, but there is not yet enough data from adult returns to tell.

In the final analysis, Connor thinks that the Snake fall chinook bonanza could eventually prove to be an example where a hatchery supplementation program does boost productivity of a natural stock. On the other hand, he noted, there has never been an example where a hatchery program has caused the collapse of a natural population.

Bill Rudolph
Extra-Large Fall Run Expected in Columbia and Snake
NW Fishletter, August 5, 2011

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